The heart is critically dependent on uninterrupted blood flow for the delivery of oxygen and nutrients and the removal of harmful products of metabolism. Ischemia leads to rapid changes in myocardial metabolism and cellular injury, the extent of the injury being dependent upon the severity of ischemia. Continued ischemia leads to total tissue necrosis in a few hours.
Reperfusion, although generally considered beneficial, causes tissue injury by several mechanisms. Clinically, in open heart surgery, heart transplantation, and reversal of heart disease, protection of the myocardium against injury by ischemia-reperfusion is an issue of utmost clinical interest. Further, exacerbation of hypoxic injury after restoration of oxygenation (reoxygenation) by reperfusion is an important mechanism of cellular injury in other types of organ transplantation and in hepatic, intestinal, cerebral, renal, and other ischemic syndromes.